De-waxed paraffin sections of AD, DLB, MS, sALS, and VD cases showed TREM2 immunoreactivity in the blood vessels and microglia surrounding β-amyloid plaques in AD, lipid-laden macrophages in subacute MS plaques, macrophages and a few mononuclear cells in subacute infarcts, and a few microglia in the spinal cord in sALS. This evidence concerns the gene TREM2 and myeloid sarcoma.